Sensors are commercially available which can produce environmental information in the form of an electrical or optical signal about the local area in which the sensor is situated. These sensors can detect just about any hazard that can be imagined. Such sensors come in many different forms, requiring different levels of electrical power and producing outputs in many different forms. In the past, such sensors have been connected directly to alarms or other readout devices to warn surrounding personnel. In some instances, the sensors have been wired to a remote location for display and analysis. Depending on the sensor output level and the distance to the remote location, amplifiers or other means are required. Unfortunately, in many cases, the wires or fiber optic cables (collectively referred to as "land lines" herein) are expensive or impractical to install, and are subject to damage and disruption at the very time during an incident when the environmental information is needed.
There are many times and locations, especially when the handling of hazardous materials are involved, where the monitoring of environmental conditions over a wide area is desirable. Sometimes the areas are so wide or noncontagious as to prohibit the economic use of land lines to connect sensors to a central location. Examples include: refineries which may cover wide areas; battlefields where the land lines are prone to damage or sabotage; dock areas which have long linear lengths separated by water; portable hazards, such as a string of moving railroad cars with hazardous cargo or a fleet of hazardous cargo carrying trucks; and large ships where long and complex electrical or fiber optic line runs can be difficult, expensive, inconvenient to install on existing ships, and subject to damage just as the environmental information is needed.
Therefore, there has been a need, especially when dealing with toxic, explosive, or legally controlled materials or substances to have a system which can enable the gathering of information from many sensors, which may be fixed or portable, over a wide area for transmittal to a central location where the information can be processed, stored and used to provide adequate warning and/or a record of extraordinary events.